Development: On 15 April Mexico’s interior ministry (Segob) issued an alert in five states after reporting that radioactive material had been stolen on 13 April from the Cárdenas municipality, in the southern state of Tabasco.

Significance: This is the third theft of radioactive material in less than two years, after one inDecember 2013and another inJune 2014. While the authorities remain unsure as to why criminal groups might have an interest in obtaining the material, serious concerns persist as to the potential threat that this practice could pose to national security.

According to the alert issued by Segob’s national civil protection system, a container holding an iridium-192 source, marked X-571, was stolen from a truck belonging to local company, Garantia Radiografica e Ingenieria. The firm notified the national nuclear security commission (Conasenusa) of the robbery yesterday. The statement warns that the substance is “very dangerous to people if removed from its container”. The alert is in place for the states of Tabasco, Campeche, Chiapas, Oaxaca and Veracruz.

Iridium-192 is used mainly for industrial applications as well as in medicine as a source of radiation to kill cancer cells. As regards its potential uses for a so-called “dirty bomb” (radiological dispersal device [RDD] - a speculative radiological weapon that combines radioactive material with conventional explosives), experts note as a drawback, that iridium-192 loses its radioactivity relatively quickly, with a half-life of 74 days.

Looking Ahead:According to the Segob statement, the defence ministry, the navy and the federal police have now also been alerted.